<form action="" id="form">
  <input type="text" name="text">
  <button>保存</button>
</form>
<ul id="root"></ul>

<script>
const key = 'logs'
const logs = JSON.parse(localStorage.getItem(key)) || []
const form = document.getElementById('form')

const render = () => {
  const root = document.getElementById('root')
  root.innerHTML = logs.map(
    log => `<li>${log.text}(${log.time})</li>`
  ).join('')
}

form.addEventListener('submit', e => {
  e.preventDefault()
  const text = form.text.value.trim()
  const log = {text, time: Date.now()}
  logs.push(log)
  localStorage.setItem(key, JSON.stringify(logs))
  render()
})

render()

</script>